Studies on the effect of diphtheria toxin on protein synthesis in mice.

Abstract

SUMMARY Mice are several orders of magnitude more resistant to diphtheria toxin than are guinea-pigs and man. Resistance is, however, relative rather than absolute, because 2000 guinea-pig lethal doses cause death of mice within 36 hr. Mice subjected to this quantity of toxin subsequently received an injection of tritiated leucine during the latter stages of the toxaemia in order to assess de novo protein synthesis in vivo. All tissues from toxin-treated mice, with the exception of skeletal muscle and kidney, incorporated 3H-leucine to the same extent as did comparable tissues of normal animals, or to a greater extent. In view of the fact that the biochemical action of diphtheria toxin on more susceptible animals is known to result in a cessation of protein synthesis, the implications of the unexpected results are discussed in terms of species resistance to toxin and the pathophysiology of diphtheritic toxaemia.